Not too long ago, I was in a chess tournament playing a very drawn out game. I entered a deep calculation mode and although the situation seemed pretty even, I realize that I can win a pawn and gain a material advantage going into the later stages of the game. I did this and eventually won the game. However, after the game, I looked over the "replay" (lols...) and found that during my deep calculation, I literally had a 1 move checkmate. I had completely overlooked it because I was so focused on winning that pawn.
You see... in game 2 of Jinro vs MVP, Jinro also had a 1 move checkmate too... all he had to do was send 1 marine down to the gold expansion... I mean, it was so obvious that the CC must have lifted somewhere because it wasn't destroyed.
Both are examples of what I like to call Tunnel Vision (or Tunnel Thinking). Sometimes, especially in high pressure situations, we become so focused on finding a solution to the task at hand that we neglect our common senses. In addition, having a game plan doesn't help either, especially when under pressure, because we end up depending on the game plan too much. I had made plans to capture that pawn, and I followed it until the end. Jinro had a very calculated game plan which he probably followed perfectly. However, sometimes we need to abandon or adjust the game plan on the spot, which may be very difficult under pressure.
Sure, having Tunnel Vision/Thinking may not be so great in the scenarios mentioned above, but it's not a terrible quality to have. I have a friend that is so focused when she studies during exam period that not even popping a paper bag next to her would deflect her attention. Needless to say, she's a student with perfect grades.